1. Field of the Invention
This invention relates broadly to optical and ophthalmic technology. More specifically, this invention relates to contact lenses having radiation absorption materials, especially visible and ultraviolet light absorbing materials.
2. Description of the Related Art
Ultraviolet radiation, i.e., radiation having wavelengths of about 200 to 400 nm, is known to be harmful to human beings in various ways. For example, several ocular pathologies have been found to result from excessive exposure to ultraviolet radiation. Further, ocular damage resulting from ultraviolet radiation is known to be cumulative. Thus, the importance of providing adequate protection of the eye from harmful ultraviolet radiation should not be underestimated.
Ultraviolet radiation absorbing coatings on spectacles and within sunglasses are well known in the art. More recently, ultraviolet radiation absorbing contact lenses and methods of fabricating these lenses have been disclosed. For example, U.S. Pat. No. 4,390,676 discloses an ultraviolet radiation-absorbing contact lens formed by copolymerizing a monomer suitable for making lenses and a compound useful in absorbing radiation having wavelengths of 340 to 450 nm. The UV absorbing compound, 2-hydroxy-4-methacryloxy-benzophenone, is incorporated into the lens' polymeric material at the molecular level. Another example of a disclosure of UV-absorbing contact lenses is U.S. Pat. No. 4,528,311. This patent discloses ultraviolet light absorbing contact lenses made of a polymeric composition comprising copolymers of 2-hydroxy-5-acrylyloxyphenyl-2H-benzotriazole with one or more other monomers copolymerizable therewith.
An example of a fundamental improvement in aforementioned UV-absorber technology is U.S. Pat. No. 4,929,250, issued to Hung, et al., which discloses a halotriazine reactive ultraviolet radiation absorbing agent employed in relatively small amounts to produce a lens having little yellowing. The agent includes a UV-absorbing component and an aqueous soluble moiety bonded to a halotriazine. Although the Hung patent discloses substantial improvements in contact lens UV-absorption technology, there is a need to increase the efficiency of incorporating UV absorbers in contact lenses.